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Plasma Antennas
Answers to RF Cafe Quiz #43

All RF Cafe quizzes would make perfect fodder for employment interviews for technicians or engineers - particularly those who are fresh out
of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons
who are going to be interviewed for a job.

This
quiz is based on the information presented in Plasma Antennas, by Theodore Anderson.Note: Some of these books are available as prizes in the monthly
RF Cafe Giveaway.

1. When the frequency of operation of a plasma antenna decreases, what is the corresponding
requirement for plasma density?

c) Plasma density must decrease

A rule of thumb is that the plasma
frequency should be about twice or greater than the operating frequency of the plasma antenna consider the plasma
antenna to behave as an effective metal antenna. (see page 4)

This property allows flat panel plasma tube arrays to be programmed as scanning
phased arrays, adaptive parabolic, or just about any other shape antenna. (see page 5)

3. How is characteristic impedance controlled in a plasma antenna?

d) All the above

The text specifically cites the plasma density's role in affecting impedance, but the plasma antenna's shape and
plasma material also determines impedance. (see page 34)

4. What commonly
available component is useful as a plasma antenna demonstrator?

a) Fluorescent bulb

Probably the most useful fluorescent bulbs are the ones with a U shape that have electrode ends which can be
placed inside a metal enclosure with only the glass tube exposed as an antenna. (see page 38)

5. What is plasma, by the way?

b) An ionized gas

Duh. (see page 45)

6. In a multiple frequency nested plasma antenna, where is the highest frequency
antenna element located relative to the lowest frequency antenna element?

b) Lowest frequency element on
the outside, highest frequency element on the inside

Placing the denser, higher frequency at the innermost
location and layering outward with progressively lower densities with correspondingly lower frequencies allows the
inner layers to see through the outer layers (see page 47)